Moderna Inc.'s respiratory syncytial virus shot, mRESVIA, demonstrated 50% efficacy in preventing RSV after 18 months, the company reported on Wednesday.

In their clinical trials, GSK's RSV vaccine Arexvy was 78% effective in preventing severe RSV over a second year and Pfizer's was 78% effective through a second RSV season.

Moderna presented the data at a meeting of the U.S. Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices. The company has previously cautioned against comparing its vaccine to those of its rivals, noting that the trials were not head-to-head and used different case definitions for RSV disease.